/*
 * Copyright 2002-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.method.annotation;

import org.springframework.core.MethodParameter;
import org.springframework.http.HttpHeaders;
import org.springframework.lang.Nullable;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.web.bind.annotation.RequestHeader;
import org.springframework.web.bind.support.WebDataBinderFactory;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.method.support.HandlerMethodArgumentResolver;
import org.springframework.web.method.support.ModelAndViewContainer;

import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;

/**
 * Resolves {@link Map} method arguments annotated with {@code @RequestHeader}.
 * For individual header values annotated with {@code @RequestHeader} see
 * {@link RequestHeaderMethodArgumentResolver} instead.
 *
 * <p>The created {@link Map} contains all request header name/value pairs.
 * The method parameter type may be a {@link MultiValueMap} to receive all
 * values for a header, not only the first one.
 *
 * @author Arjen Poutsma
 * @author Rossen Stoyanchev
 * @since 3.1
 */
public class RequestHeaderMapMethodArgumentResolver implements HandlerMethodArgumentResolver {

    @Override
    public boolean supportsParameter(MethodParameter parameter) {
        return (parameter.hasParameterAnnotation(RequestHeader.class) &&
                Map.class.isAssignableFrom(parameter.getParameterType()));
    }

    @Override
    public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
                                  NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {

        Class<?> paramType = parameter.getParameterType();
        if (MultiValueMap.class.isAssignableFrom(paramType)) {
            MultiValueMap<String, String> result;
            if (HttpHeaders.class.isAssignableFrom(paramType)) {
                result = new HttpHeaders();
            }
            else {
                result = new LinkedMultiValueMap<>();
            }
            for (Iterator<String> iterator = webRequest.getHeaderNames(); iterator.hasNext(); ) {
                String headerName = iterator.next();
                String[] headerValues = webRequest.getHeaderValues(headerName);
                if (headerValues != null) {
                    for (String headerValue : headerValues) {
                        result.add(headerName, headerValue);
                    }
                }
            }
            return result;
        }
        else {
            Map<String, String> result = new LinkedHashMap<>();
            for (Iterator<String> iterator = webRequest.getHeaderNames(); iterator.hasNext(); ) {
                String headerName = iterator.next();
                String headerValue = webRequest.getHeader(headerName);
                if (headerValue != null) {
                    result.put(headerName, headerValue);
                }
            }
            return result;
        }
    }

}
